1. Field of the Invention
This invention generally relates to an identification module for an inkjet print head, and more particularly to an identification module having combination logic circuit for an identification circuit of an inkjet printer.
2. Description of Related Art
FIG. 5 is a schematic diagram of a conventional identification circuit for an inkjet printer, disclosed by Hewlett-Packard Company in U.S. Pat. No. 5,363,134 entitled “Integrated circuit printhead for an ink jet printer including an integrated identification circuit”. The identification module 526 provides the identification information of the inkjet print head 52 for the inkjet printer 50. The inkjet print head is disposed inside the inkjet printer 50. The inkjet printer 50 includes a controller 502 for controlling the operation of the inkjet 50, and a head drive circuit 504 for driving the inkjet print head 52. The inkjet printer 50 further includes three buses 506A–506C for example coupled between the controller 502 and the head drive circuit 504 for transmitting the digital control signals from the controller 502 to the head drive circuit 504, and for the head drive circuit 504 to output the corresponding analog voltage pulse to the circuits of the inkjet print head 52. The inkjet print head 52 includes an array circuit 522 for heating the ink based on the output signal of the head drive circuit 504 to eject the ink out of the nozzle. The identification module 526 provides the identification information of the inkjet print head 52 for the inkjet printer 50. The temperature sensing circuit 524 provides the temperature-related and other information relevant to the inkjet print head for the inkjet printer 50. A plurality of row lines (or so-called address lines) 528A and column lines (not shown in FIG. 5) are disposed between the head drive circuit 504 and array circuit 522. The head drive circuit 504 selects and drives the devices of the array circuit 522 via these row lines 528A and column lines. The detailed operation will be described as follows.
FIGS. 6A and 6B show a diagram of the array circuit and a circuit of a resistor unit, respectively. The array circuit 522 includes a plurality of resistor units 69 arranged in a plurality of rows and columns for heating the ink to eject out the ink through the nozzle. A plurality of row lines (e.g., A0–A5) and column lines (e.g., power supply lines P0–P5) are connected to the array circuit 522 to selectively provide the energy for the resistor unit 69 so that the selected resistor unit 69 can generate heat to vaporize the ink and eject drops of ink out of nozzles. Each resistor unit 69 includes a resistor 63 and a transistor 64, wherein the transistor 64 is coupled to one of the address lines A0–A5 to control the current flowing through the resistor 63. When a positive voltage is supplied respectively to the row line and the column line connected to the resistor unit 69, the transistor will be turned on and the current will flow through the resistor 63. Hence, the resistor 63 will vaporize the ink and eject drops of ink out of nozzles.
FIG. 7 is a conventional identification module. The identification module 526 is coupled to a plurality of row lines (e.g., A1–A13) and includes a plurality programmable paths consisting of a plurality of fuses (e.g., F1–F13) and a plurality of transistors (e.g., Q1–Q13). Each programmable path includes a fuse series-connected to the gate of a corresponding transistor. Each programmable path provides one-bit identification code for the inkjet printer 50. The one-bit identification code is “1” or “0” depending on whether the fuse is blown or not. Hence, the combination of the one-bit identification codes can provide different identification information for the inkjet printer 50.
In brief, the conventional identification circuit requires a row line for one bit identification code. Further, only one row line can be at logic high at a time. Therefore, to provide more identification codes, the cost of the identification circuit is higher and the size of the identification circuit becomes larger.